This invention relates to controlled force actuating systems and more particularly, to an actuating system in which an actuating force is supplied by controlled release of a loaded spring. The actuating system is particularly applicable to the development of normal forces for friction devices such as power transmitting clutches or friction brakes but is also useful in other applications.
Numerous diverse types of mechanisms employ a force acuator system by which energy stored in a spring is released to develop a loading force on a component and by which the loading force is removed by restoring energy to the spring. Most commonly, the force actuating system uses a control device having a built-in mechanical advantage so that the control force required to remove the loading force, or to control its release, is relatively small as compared with the loading force. Force actuator systems of this basic type have a wide range of applications including, by way of example only, friction devices such as clutches and brakes, fluid control valves, hand operated devices such as clamps, closure retaining mechanisms, and other such spring actuated mechanisms.
Automotive power transmitting or starting clutches represent one of the more challenging applications of controlled force actuating systems in which a relatively large amount of energy stored in a spring must be controlled during release and restorers to the spring. Such clutches employ frictionally engaged torques tansmitting components which must remain fixed to each other by the spring force without slippage when fully engaged, and which must be engaged under control to avoid an abrupt transition of power transmission during engagement. Traditionally, the relatively large force actuating springs of automotive clutches have been operated by control systems involving levers, ball ramps or other force reduction devices by which the actuating spring may be controlled by a foot pedal, for example.
The conventional contol systems for automotive starting clutches are not only complex and space consuming, but also, the, are not suited to automation because of the large amounts of energy required for their operation. In this latter respect, the development of on-board computers in automotive vehicles has given rise to much interest in automating the operating of starting clutches and the power transmissions with which they are used. In spite of many recent attempts to accomplish such automation, the energy requirements to retract and control the release of the clutch spring have been a major obstacle.
Hence, there is an acute need for a controlled force actuating system by which a large spring force can be exerted but which can be operated by a relatively small amount of contol energy. This need exists not only in automatic clutch applications, but also in numerous other applications where spring stored energy is released and retacted to and from a load.